1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing cathode ray tube (CRT) display devices.
2. Background Description
A CRT display device, such as a television receiver or a computer visual display unit, comprises a CRT connected to associated drive circuitry all enclosed by a housing. The CRT comprises an electron gun assembly directed at a phosphor coated screen, a final anode adjacent the screen, and focus and grid electrodes adjacent the electron gun assembly. Electromagnetic deflection coils are provided in a yoke around the CRT between the screen and the electron gun assembly. The drive circuitry typically comprises a video amplifier connected to the electron gun assembly. In a typical colour CRT display, the electron gun assembly has three electron guns each assigned to a different one of the three primary colours, red, green and blue. Each electron comprises a thermionic cathode. The three electron guns are each connected to a different one of the three video channels in the video amplifier. The drive circuitry also includes line and frame deflection circuits for generating line and frame scan currents in a deflection yoke of the CRT. An Extra High Tension (EHT) voltage generator of the drive circuitry supplies DC drive voltages to the final anode, focus electrode and grid electrodes. In operation, the EHT generator generates a relatively high voltage between the final anode and the cathodes. Electrons from the cathodes are thus accelerated in beams from the cathodes to the screen. At the screen, the electrons excite the phosphors to generate a light output. The beams are scanned in a raster pattern by line and frame deflection fields produced via the line and frame deflection coils. The video amplifier modulates the electron beams in response to input red, green and blue video signals from an external video source such as a personal computer system unit. The raster pattern is synchronised to the input video by input synchronisation (sync) signals supplied to the deflection circuitry by the external video source.
The drive circuitry of some display devices comprises a display processor in the form of a micro-controller which is programmed to control, via digital to analog convertors the video and deflection sub-systems of the drive circuitry.
Conventionally, display devices as hereinbefore described are each assembled on a production line by connecting the CRT to the drive circuitry and then iteratively adjusting display operating parameters such as colour balance and picture geometry to specified production values prior to product shipment. The iterative adjustments consume significant manufacturing time, tending to increase overall product cost. It would be desirable, in the interests of reducing manufacturing time and thus cost, to integrate CRT test measurements from tests conducted by the CRT supplier into the adjustment process applied to the assembled display device prior to shipment.
U.S. Pat. No. 4,377,890 describes a method of CRT manufacture using a machine readable coded marking in which a unique, coded marking in applied to the exterior of a part of a CRT manufactured for the purpose of tracking the location of the part on a production line, adding additional parts to the parts, or testing an assembled CRT including the part.